Kolkman



Jan. 31, 1956 o. KOLKMAN GAS-FILLED ELECTRIC DISCHARGE TUBE Filed March 5, 1952 INVENTOR. DIRK KOLKMAN AGEXI.

GAS-FILLED ELECTRIC DISCHARGE TUBE Dirk Kolkman, Eiudhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee This invention relates to gas-filled electric discharge tubes. More particularly, the invention relates to elongated positive column gas-filled electric discharge tubes comprising an auxiliary electrode for starting purposes.

It is an object of the invention to reduce the starting or igniting voltage of tubes of the foregoing type.

This and further objects of the invention will appear from the description that follows.

According'to the invention, an elongated positive column gas-filled electric discharge tube comprising an elongated envelope which may have a coating of fluorescent material on an inner surface thereof, encloses a pair of main electrodes disposed at opposite ends of the envelope. An auxiliary electrode comprising a long thin electrically conducting strip extends along an inner wall of the envelope and is electrically connected to one of the main electrodes. Conducting leads for providing exter nal circuit connections to the main electrodes and for connecting the auxiliary electrode to a main electrode are provided with an electrically insulating coating. With such an arrangement, an arc discharge will occur within such a tube at a lower voltage.

The invention will now be described with reference to the accompanying drawing wherein the sole figure shows a cross-sectional view of an electric discharge tube in accordance with the invention.

Referring to the 'drawing, 1 designates an elongated positive column electric discharge tube connected through an inductor 2 to terminals 3 and 4 of a current supply. The inner wall of the tube 1 is coated with a layer of fluorescent material 5.

Two main electrodes 10, disposed at opposite ends of the tube 1, are formed of a refractory wire coated with an electron-emissive active substance, for example, strontium and barium compounds. Two long thin auxiliary electrodes 6 extending along and secured to inner facing surfaces of the tube 1 are connected, respectively, to one of the main electrodes 10. The auxiliary electrodes 6 may be formed of any electrically conducting material, for example, graphite, enamel and a binder. Each of the auxiliary electrodes 6 is connected to one of the main electrodes through a metal ribbon 7 and a short metal wire 8 which is connected to one of two current supply members 9 for the main electrode 10. In other words, electrical connection between the main electrode 10 and the long thin auxiliary electrode 6 is provided by one of the current supply members 9 for the main electrode 10 which is connected to a metal wire 8 which, in turn, is connected to one end of a metal ribbon 7, the other end of which is connected to the auxiliary electrode 6. The main electrode 10 is supported by;the current supply members 9 in a conventional vitreous bead. V

V In order to clarify the description, the auxiliary electrodes 6 have been shown as diametrically opposite to one another so that their relative spacing is equal to the internal diameter of the tube 1. However, it will be obvious that this spacing may be made considerably smaller.

The current supply members 9 for the main electrodes United States PatentO 'turns into an arc discharge.

10 and the connecting members 8, and 7 between the main electrodes 10 and the auxiliary electrode 6 are coated with electrically insulating layers 12 13 and 14, respectively. These layers 12, 13 and 14 may be made, for

example, of potassium water glass, a glazing, alundum, or

any other like insulating material.

Upon connecting terminals 3 and 4 to a suitable power supply a glow discharge will occur between a main electrode 10, which serves as a cathode at that instant, and the unconnected end of the auxiliary electrode 6 to which it is not electrically connected. This glow discharge will travel along the auxiliary electrode 6 to the other main electrode 10. The main electrodes 10 are heated by the By coating all of the non activated parts of the tube 1, i. e., the parts of the tube which do not contribute to producing the arc discharge but which are, nevertheless, at the same potential as the main electrodes 10 with an insulating coating, they are made inaccessible to the glow discharge, which, consequently, concentrates on the activated part of the electrodes, i. e., the barium and strontium compounds. The result is that the transition of glow discharge to are discharge takes place at a lower voltage.

In one example, a tube having a length of about cms.; an internal diameter of about 35 mms.; filled with containing, furthermore, a small quantity of mercury; two long thin auxiliary electrodes, each having a width of about 3 mms. and being separated from each other by about 15 mms.; had its starting voltage reduced from about 210 volts to about volts by having its nonactivated parts coated with an insulating layer in accordance with the invention.

While we have thus described our invention with specific examples and embodiments thereof, other modification will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

What I claim is:

(References on following page) Patented Jan. 31, 1956 V 4 References Cited in the file of this patent v 2,444,397 Cram June 29, 1948 2,445,692 P0116! et a1 July 20, 1948 UNITED STATES PATENTS 2,491,854 Force Dec. 20, 1949 2,009,223 w JulY 23, 1935 2,504,498 Clack Apr. 18, 1950 2,056,613 Mltchell 1936 5 2,503,11 Lemmas M 15, 1950 2,094,647 Freitag 5, 1937 2,542,352 peters F 20 1951 2,266,800 Reed Dec. 23, 1941 V r 2,291,965 Jancke Aug. 4, 1942 

